High Idle

[Ironhyde]

Hi all, I am new to forum, and we have only had cars for about 6 months. Been lurking on here and getting ideas when possible (great forum!). I am having an issue with one of our cars, sealed motor, the idle keeps going up as the car warms up, and if I adjust the idle screw down to where it should be it dies. At first I though it was dirt in carb, (was going to replace foam in fuel cell, and fuel line, as we run pump gas with ethanol) but I cleaned it best I could, and it is still doing it. When you come off the track the motor is reving, and I have to keep blipping the throttle to get it to idle down. I don't know if there is some vaccum leak? Ignition box issue?
I know this will seem like a vague description to some, but maybe someone else has had similar issue.

Thanks for any advice!

[VMS Motorsports]

Which ignition box are you running?
Is your throttle cable free? Could be hanging up inside the sleeve if pulled too tight somewhere

[canabl]

We had same issue with two of our cars here and one turned out to be a blown gasket between case and cylinder block from a snapped head stud and the second was a damaged cam journal in the head. Hopefully these are not the same cause for yours.
The new car we have and three others we have tuned seem to need the choke pulled out a touch whilst idle for some time before the engine warms up. We run the carbs with normal 2 1/2 - 3 turns on the idle screws on top of carb and usually after the first heat the idle is perfect and no choke required after that.

[Ironhyde]

Jim,
 We are running red boxes. The throttle cable seems free, I might lube it a bit, but it does it sitting still, when engine is warm also. 

I hope it's not a head gasket! The motor runs great at full throttle on the track under load, so I don't think head gasket. 

[VMS Motorsports]

I know nothing about the red box ignition, can't help you there.

I mention the throttle cable because before nationals I put a new one in, and it was just a tad too tight, so at times, it would hold the carbs open, blip the throttle and it was fine. Got to looking, and it was flexing the firewall just enough

[justfreaky]

Could be something simple like a speck of dirt or vaccum leak. Could be as Jim sugests and is related to the throttle cable. Take your time and go through the easy fixes first. If still a problem, start at the beginning and work your way through the problem. Know that sounds easier than it could be. Most times it is a simple fix.

Steve

[Legends16]

Could this be a carb syncing issue? Could is be a jetting issue?

Ive had idling issues in the past. One time I lost one out of the four small caps that clamp onto the carbs. I think it caps off the vacuum lines? Im not entirely sure what it was for.

I found I had been running carbs that were for the most part stock bike carbs. When I had my motorcycle guy tuned them up It made a big difference in Idle, starting and throttle responce.

Just throwing some ideas out there.

Best of  luck!

[Earnst85]

Another thing to check is that your clamp rings (hold the carbs to the motor intake) are not rotated and either the rings or screws are interfering as not to allow the throttle to be completely off.

If that is the case, when you set your idle, the throttle is already open a little and then when it warms up, the idle will be way too fast.

[Earnst85]

We have good success syncing carbs with a Bike Master Carb sync tool... if they need syncronized.

http://www.amazon.com/BikeMaster-29-03J-CARB-SYNCHRONIZING-KIT/dp/B005G5QVW0

[Ironhyde]

It could very well be vaccum issue, as you guys are stating! That seems like the symptoms, because it is just sitting there in the shop, and it will idle for a couple of minutes, then all the sudden it starts increasing the idle.

Where are the vaccum caps or block offs?

 I put my hand over each of the carbs with the air filters off, and they all have good vaccum, but I don't see any caps or plugs at all -

Legends16 where on the carb are they (i.e. back side toward motor, on fuel rail, on outside toward fuel line in, bottom of bowl?)

No doubt I need these carbs synced, and probably jetted by professional, it's running rich, and I get a lot of backfire pop when I rev it).

Justfreaky - I am hoping for easy - simple fix! But you know how that goes....

Thanks everyone, I will try a few more things, hoping to race sunday, so I am hoping for quick fix.

[Earnst85]

The caps are on the motor top behind the carb's heat shield. Depending on what coil mounting plate you have, you may have to move it to the side to get to them.

[VMS Motorsports]

To quickly check the carb boots, spray some WD40 on each one while engine is running. If it changes anything, then you need a new boot. then check the other three

[amp racing]

make sure the carb slides are not sticking... popping and throttle idle could be if one was sticking... valve adjustment and sync..

joe

[Legends16]

The caps are on the motor top behind the carb's heat shield. Depending on what coil mounting plate you have, you may have to move it to the side to get to them.

Eanst85 beat me to it.  I have to remove the coil bracket to see them on my car. Let me know if you cant find them and Ill try and shoot you a picture .

Definatly check them and have the carbs synced.

[Ironhyde]

Earnst85 - I checked out that sync tool, and ordered one, found cheaper ones, but that kit has more connector length options, so the sync is going to happen.  Thanks!

Joe - I will check behind the plate the coils are on for the vaccum caps - (I was cleaning back there.....) the slides are not sticking, I checked, and sprayed with some good carb cleaner.

Jim - I will try the WD-40 trick also (The boots do look a little dry..probably need to order some from your web site, besides I need some new stickers, the last ones went when I rolled it and had to replace the body.)

Thanks guys!